Abstract
In the isolated right atrium of the rabbit heart the influence of the atrial myocardium on impulse formation in the sinus node was investigated. Under normal conditions the pacemaker (earliest activation) was located in the center of the node where fibers with the highest rate of diastolic depolarization were found. After disconnection of the atrium from the sinus node spontaneous cycle length decreased from a mean of 348 ms to a mean of 288 ms (−18%) in all experiments (n=15). This was accompanied by a shift of the pacemaker from the nodal center towards the border zone. By means of multiple microelectrode impalements changes in action potential configuration were studied. After disconnection of atrium and sinus node the rate of diastolic depolarization of fibers in the border zone was increased from a mean of 26 mV/s to a mean of 78 mV/s, whereas in the center of the sinus node no increase was found (mean: 52 mV/s). It was concluded that the fibers in the border zone of the sinus node are better pacemaker fibers than in the nodal center. However under normal conditions the intrinsic pacemaker properties of the border zone fibers are electronically depressed by the connected atrial myocardium.
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Antzelevitch C, Jalife J, Moe GK (1982) Electrotonic modulation of pacemaker activity. Further biological and mathematical observations on the behavior of modulated parasystole. Circulation 66:1225–1232
Bleeker WK, Mackaay AJC, Masson-Pevet M, Bouman LN, Becker AE (1980) Functional and morphological organisation of the rabbit sinus node. Circ Res 46:11–22
Bonke FIM (1973) Electrotonic spread in the sinoatrial node of the rabbit heart. Pflügers Arch 339:17–23
Bonke FIM (1980) Electrophysiology of the sinus node and atrial pacemakers. In: Little RC (ed) Physiology of atrial pacemakers and conductive tissues. Futura Publishing Company, Mount Kisco NY, pp 171–186
Bonke FIM, Steinbeck G, Allessie MA, Mackaay AJC, Slenter VAJ (1982) The electrophysiological effects of cardiac glycosides on the isolated sinus node of the rabbit. In: Paes de Carvalho A, Hoffman BF, Lieberman M (eds) Normal and abnormal conduction in the heart. Futura Publishing Company, Mount Kisco NY, pp 347–361
Bouman LN, Gerlings ED, Biersteker PA, Bonke FIM (1968) Pacemaker shift in the sinoatrial node during vagal stimulation. Pflügers Arch 302:255–267
Bouman LN, Mackaay AJC, Bleeker WK, Becker AE (1978) Pacemaker shifts in the sinus node: Effects of vagal stimulation, temperature, and reduction of extracellular calcium. In: Bonke FIM (ed) The sinus node. Structure, function and clinical relevance. Martinus Nijhoff Medical Division, The Hague, pp 245–257
Bukauskas FF, Veteikis RP, Gutman AM, Mutskus KS (1977) Intracellular coupling in the sinus node of the rabbit heart. Biofizika 22:108–112
Capelle FJL van, Durrer D (1980) Computer simulation of arrhythmias in a network of coupled excitable elements. Circ Res 47:454–466
DeHaan RL, Fozzard HA (1975) Membrane response to current pulses in spheroidal aggregates of embryonic heart cells. J Gen Physiol 65:207–222
DeHaan RL, Hirakow R (1972) Synchronization of pulsation rates in isolated cardiac myocytes. Exp Cell Res 70:214–220
Deleze J (1970) The recovery of resting potential and input resistance in sheep heart injured by knife or laser. J Physiol 208:547–562
Delmar M, Jalife J, Michaels DC (1986) Effects of changes in excitability and intercellular coupling on synchronization in the rabbit sino-atrial node. J Physiol 370:127–150
De Mello WC (1972) The healing-over process in cardiac and other muscle fibers. In: De Mello WC (ed) Electrical phenomena in the heart. Academic Press, New York, pp 323–351
De Mello WC (1976) Influence of the sodium pump on intercellular communication in heart fibres: effect of intracellular injection of sodium ion on electrical coupling. J Physiol 263:171–197
De Mello WC (1983) The influence of pH on the healing-over of mammalian cardiac muscle. J Physiol 339:299–307
Griepp EB, Bernfield MR (1978) Acquisition of synchronous bcating between embryonic heart cell aggregates and layers. Exp Cell Res 113:263–272
Irisawa A (1978) Fine structure of the small sinoatrial specimen used for the voltage clamp experiment. In: Bonke FIM (ed) The sinus node. Structure, function and clinical relevance. Martinus Nijhoff Medical Division, The Hague, pp 311–319
Jalife J (1984) Mutual entrainment and electrical coupling as mechanisms for synchronous firing of rabbit sino-atrial pacemaker cells. J Physiol 356:221–243
Jalife J, Michaels DC (1985) Phase-dependent interactions of cardiac pacemakers as mechanisms of control and synchronization in the heart. In: Zipes DP, Jalife J (eds) Cardiac electrophysiology and arrhythmias. Grune and Stratton, Orlando, pp 109–119
Jongsma HJ, Masson-Pevet M, Hollander CC, Bruyne de J (1975) Synchronization of the beating frequency of cultured rat heart cells. In: Lieberman M, Sano T (eds) Development and physiological correlates of cardiac muscle. Raven Press, New York, pp 185–196
Kodama I, Boyett MR (1985) Regional differences in the electrical activity of the rabbit sinus node. Pflügers Arch 404:214–226
Kreitner D (1985) Electrophysiological study of the two main pacemaker mechanisms in the rabbit sinus node. Cardiovasc Res 19:304–318
Mackaay AJC (1980) Frequency regulation in the sinus node. PhD Thesis University of Amsterdam
Masson-Pevet M, Bleeker WK, Mackaay AJC, Bouman LN (1979) Sinus node and atrium cells from the rabbit heart: a quantitative electron microscopic description after electrophysiological localization. J Mol Cell Cardiol 11:555–568
Noma A, Irisawa H (1976) Membrane currents in the rabbit sino-atrial node cell as studied by the double microelectrode method. Pflügers Arch 364:45–52
Sano T, Yamagishi S (1965) Spread of excitation from the sinus node. Circ Res 16:423–430
Sano T, Sawanobori T, Adaniya H (1978) Mechanism of rhythm determination among pacemaker cells of the mammalian sinus node. Am J Physiol 235:H379-H384
Seyama I (1976) Characteristics of the rectifying properties of the sino-atrial node cell of the rabbit. J Physiol (Lond) 255:379–397
Steinbeck G, Bonke FIM, Allessie MA, Lammers WJEP (1980) The effect of ouabain on the isolated sinus node preparation of the rabbit studied with microelectrodes. Circ Res 46:406–414
Strauss HC, Bigger JT (1972) Electrophysiological properties of the perinodal fibers. Circ Res 31:490–506
Takayanagi K, Jalife J (1986) Effects of digitalis intoxication on pacemaker rhythm and synchronization in rabbit sinus node. Am J Physiol 250:H567-H578
Toda N, Shimamoto K (1968) The influence of sympathetic stimulation on transmembrane potentials in the SA node. J Pharmacol Exp Ther 159:298–305
Weingart R (1977) The actions of ouabain on intercellular coupling and conduction velocity in mammalian ventricular muscle. J Physiol 264:341–365
Ypey DL, Clapham DE, De Haan RL (1979) Development of electrical coupling and action potential synchrony between paired aggregates of embryonic heart cells. J Membr Biol 51:75–96
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Kirchhof, C.J.H.J., Bonke, F.I.M., Allessie, M.A. et al. The influence of the atrial myocardium on impulse formation in the rabbit sinus node. Pflugers Arch. 410, 198–203 (1987). https://doi.org/10.1007/BF00581916
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DOI: https://doi.org/10.1007/BF00581916